Method of stabilizing raw gasoline



Dec. 22, 1953 B. c. BARNES METHOD oF STABILIZING RAW GASOLINE Patented Dec. 22, 1953 UNITED STATES T F F I CE METHOD F STABILIZIN G RAW GASOLINE Brunner C. Barnes, Dallas, Tex., assignor, by mesne assignments, to Socony-Vacuum Gil Company, Incorporated, New York, N. Y., a

corporationof New York Application July 1, 1950, Serial No. 171,620

4 Claims.

Hydrocarbon gas containing butane, pentane,

hexane and perhaps heavier hydrocarbons in addition to lighter hydrocarbons such as propane, ethane, or methane, may be treated in a variety of ways to separate and recover therefrom a heavy hydrocarbon fraction. One way of obtaining a heavy hydrocarbon fraction from a wet gas, called a wet gas because of the presence of heavy liquid hydrocarbons that may be obtained therefrom in the liquid phase, is by the compression-refrigeration method which involves compression and cooling of the gas whereby the heavy hydrocarbons enter the liquid phase and separation of the liquid hydrocarbons from the gaseous hydrocarbons is thereby effected. Depending upon the extent of the compression and the cooling and the composition of the wet gas, the composition of the liquid phase, or gasoline, will vary. Thus, gas obtained from a petroleum hydrocarbon reservoir, for example, may be treated by compression and cooling to obtain gasoline containing pentane and higher hydrocarbons, butane and higher hydrocarbons, or propane and higher hydrocarbons. Hereinafter, the liquid phase obtained by compression and cooling will be termed gasoline irrespective of its composition. The raw gasoline obtained by compression and cooling is wild, i. e., contains some of the lighter hydrocarbons of the Wet gas which are undesired in the nished product, and the raw gasoline must be treated, or stabilized, to remove the light In accordance with the invention, a wet gas is treated by compression and refrigeration to obtain raw gasoline, the raw gasoline is heated in a heating zone to an extent suilicient to vaporize the-undesired light hydrocarbons, the vaporized hydrocarbons are contacted with cold raw gasoline supplied from the coinpression-refrigeration steps, the raw gasoline after contacting with the Vaporized hydrocarbons is passed to the heating zone, the vaporized hydrocarbons after contacting with the cold raw gasoline are recycled to the compression-refrigeration steps, and stabilized hydrocarbons and provide the finished product.

Heretofore, the raw gasoline has been stabilized by fractionation. However, fractionation involves condensation of the vaporous overhead to provide the necessary reflux, and requires the use of condensers, reflux accumulators, pumps, and reflux control equipment.

It is an object of this invention to provide a method for stabilizing the liquid hydrocarbon phase obtained from wet gas bythe compressionrefrigeration method. It is another object of this invention to reduce the cost of stabilizing raw gasoline obtained from Wet gas by the corn-v pression-refrigeration method. It is another object of this invention to reduce the amount of equipment required for stabilizing raw gasoline obtained from wet gas by the compression-refrigeration method. Further objects of the invention will become apparent from the following detailed description thereof.

gasoline is recovered from the heating zone.

Referring now to the accompanying figure which is a schematic fiowsheet illustrating one embodiment of the invention, wet gas enters the system through line it. The gas may be wet natural gas from a subterranean petroleum hydrocarbon reservoir, wet gas obtained from a petroleum rening operation, such as cracking still gas, or any other type of gas containing hydrocarbons that may be separated therefrom in the liquid phase by compression and cooling. f he flowsheet will be described in connection with the treatment of a wet natural gas to obtain a gasoline product containing propane and the heavier hydrocarbon components of the gas although it will be understood that the process is applicable to the treatment of a wet gas to obtain a gasoline product having any desired hy" drocarbon as the lowest boiling component thereof. The gas entering through line iii is compressed in low stage compressor il to a pressure which may be, for example, about pounds per square inch gage and is then passed through line Vl2 to low stage cooler i3 wherein the temperature is reduced by indirect heat exchange with water to about F., for example. As a result of the compression in compressor ii and cooling in cooler i3, liquid hydrocarbons are condensed from the gas and the mixture of gas and liquid hydrocarbons is passed through line it to low stage accumulator i5. The liquid hydrocarbons are removed from the accumulator through line 2i) and the gas is removed through line 2i.

The gas in line 2l is passed to high stage compresser 22 Where the pressure is increased to about 265 pounds per square inch gage, for example, and is then passed through line 23 to high stage cooler 2li where the temperature is reduced by indirect heat exchange with water to about 95 F., for example. Additional liquid hy drocarbons are condensed in the high stage compressing and cooling operations and these hydrocarbons along with the remaining gas are passed through line 25 to high stage accumulator 3d,

The liquid hydrocarbons are removed from the accumulator through line 3l and the gas is removed through line 32.

The gas in line 32 still contains hydrocarbons, such as propane and butano, that may be condensed to the liquid phase by cooling to a lower temperature. However, the gas may also contain water vapor which, upon additional cooling of the gas, will freeze and condense or form hydrocarbon hydrates with resultant clogging of lines and equipment. Accordingly, the gas is passed to dehydration contactor 33 wherein it is contacted with a suitable type or" desiccant to remove the water vapor therefrom. The dried gas is then passed through line 3 to refrigeration chiller 35 where it is cooled to a temperature of about 9 F., for example, by indirect heat exchange with A any suitable type of refrigerant commonly employed for the purpose. As a result of the refrigeration, practically all of the propane and any heavier hydrocarbons are converted to the liquid phase. The gas and the condensed hydrocarbons are then passed through line il to refrigeration accumulator 1li from which the liquid hydrocarbons are withdrawn through line 2. The residual gas is withdrawn through outlet line 43 for utilization as desired.

The liquid hydrocarbons in lines 3i and 2 are combined and passed through line i3 to condensate flash tank dfi wherein the pressure is decreased to about 40 to 50 pounds per square inch gage, for example, whereby a Iportion of ethane and methane dissolved in the condensed hydrocarbons is released from solution. The ethane and methane are removed from the top of the accumulator through line l5 and are passed to line 2i for admixture with the gas. entering high stage compressor 22 whereby any propane or heavier hydrocarbons removed from solution along with the methane and ethane are recovered in the liquid streams in lines 3i and i2. The liquid hydrocarbons leave the condensate flash tank through line Ell.

The liquid hydrocarbons in lines 5B and 2B comprise the raw gasoline product. The raw gasoline in line 2li contains ethane and methane dissolved therein and the raw gasoline in line 5B also contains ethane and methane dissolved therein, the release of ethane and methane from solution in condensate flash tank 64 not being complete. The raw gasoline streams are combined and passed through line 5l to stabilizer 52. Stabilizer 52 comprises a stripping column 53 and a reboiler 54, the stripping column being provided with a pressure controller 55 on gas outlet line 56, and the reboiler being provided with a heater 51, which may be a steam coil, and a temperature controller S9 operating valve 6i on the inlet line to the heater. The stripping column may be a packed tower or a tray or bubble plate tower and should have a stripping eiciency of two or more theoretical plates. i

The raw distillate gasoline passes downwardly through the stripping column and enters the reboiler wherein it is heated by means of the heater 51. The amount of heat provided by heater 51 is sufficient to maintain the temperature of the liquid hydrocarbons in the reboiler at a point such that, under the pressure at which the stabilizer is being operated, the ethane and methane will be vaporized from the liquid hydrocarbons and form a gaseous phaseV passing upwardly through the stripping column 53. For example, with the stabilizer operating at 26 pounds per square inch gage the temperature is maintained at about 75 F. Temperature controller 6D is connected by lead line 62 to the reboiler and serves to maintain the desired temperature, by opening and closing valve 6l to which it is connected by lead line B3, in accordance with well known principles. The gas phase containing the ethane and methane vaporizing from the liquid hydrocarbons will carry with it a portion of vaporized propane and higher hydrocarbons. The gas phase passing upwardly through the stripping column 53 countercurrently contacts the downwardly flowing stream of cold raw gasoline entering the column through line 5i, whereby' the countercurrently owing cold raw gasoline acts as redux and selectively resorbs the propane and heavier hydrocarbons from the upwardly flowing gas phase.

The ethane and methane are removed substantially entirely from the'gasoline by the heating in reboiler Sli. However, the propane and heavier hydrocarbons are not entirely removed from the gases flowing upwardly through the stripping -column by the downwardly owing stream of cold raw distillate gasoline, and, further, the upwardly flowing gases vaporize some of the propane and heavier hydrocarbons from the raw distillate gasoline. Accordingly, the upwardly flowing gases, after contacting with the downwardly flowing cold raw distillate gasoline, are removed from the column through line 5S and admixed with the inlet gas in line Iii whereby the propane and heavier hydrocarbons are recovered by passage through the compression-reirigeration system. The stabilized gasoline is removed from the stabilizer through line Bil.

Various modifications in the above described procedure may be made by those skilled in the art. For example, the compression and cooling of the gas may be conducted in a greater or lesser number of stages. Further, the extent or the compression and cooling may be varied to obtain raw gasoline as liquid `product having different compositions with respect to the light constituents thereof. Also, by varying the temperature and pressure of the liquid in the reboiler 5d, the composition of the stabilized gasoline can be varied. Other modifications will suggest themselves to those skilled in the art.

Having thus described my invention, it will be understood that such description has been given by way of illustration and example and not by way of limitation, reference for the latter purpose being had to the appended claims.

I claim:

l. A process for the separation and recovery of a stabilized liquid fraction from a wet hydrocarbon gas mixture comprising passing a feedv stream of said gas to a first compression zone and to a first cooling zone, compressing and cooling said gas in said compression zone and said cooling zone to a pressure and temperature to condense from said gas a cold liquid hydrocarbon fraction, passing said gas and said cold liquid fraction to a rst separation zone, separating uncondensed gas from said cold liquid fraction in said rst separation zone, removing cold liquid fraction from said rst separation zone, passing directly to a gas-liquid contact zone said cold liquid fraction at a temperature not substantially higher than its temperature in said rst separau tion zone, removing uncondensed gas from said first separation zone, passing said gas from said iirst separation zone to a second compression zone and to a second cooling zone, compressingY and cooling said gas in said second compression zone and said second cooling zone to a pressure and temperature to condense from said gas/a cold liquid hydrocarbon fraction, passing said gas and said cold liquid fraction to a second separation zone, separating uncondensed gas from said liquid fraction in said second separation zone, removing unoondensed gas from said second separation zone, removing said cold liquid fraction from said second separation zone,v passing said cold liquid fraction from said second separation zone to a pressure reduction zone, reducing the pressure on said cold liquid fraction in said pressure reduction zone to separate a gas phase therefrom, removing said gas phase from said pressure reduction zone, admixing said gas phase removed from said pressure reduction zone with said gas entering said second compression and cooling zones, removing said liquid fraction from said pressure reduction zone, passing said liquid fraction to said gas-liquid contact zone, passing said liquid fractions through said gasliquid contact zone to a heating zone, heating said liquid fractions in said heating zone to stabilize said liquid fractions by vaporizing therefrom a gas phase containing undesired light hydrocarbon, passing said gas phase through said gas-liquid contact zone in countercurrent contact with only said liquid fractions passing through said gas-liquid contact zone, removing said gas phase from said gas-liquid contact zone, passing the entire amount of said gas phase rcmoved from said gas-liquid contact zone directly to said rst compression zone, and recovering a stabi ized liquid fraction from said heating zone.

`2. A process for the separation and recovery of a stabilized liquid fraction from a wet hydrocarbon gas mixture comprising passing a feed stream of said gas to a rst compression zone and to a iirst cooling zone, compressing and'cooling said gas in said compression zone and said cooling zone to a pressure and temperature to condense from said gas a cold liquid hydrocarbon fraction, passing said gas and said cold liquid fraction to a rst separation zone, separating uncondensed gas from said cold liquid fraction in said separation zone, removing cold liquid fraction from said rst separation zone, passing directly to a gas-liquid contact zone, said cold liquid fraction at a temperature not substantially higher than its temperature in said first separation zone, removing uncondensed gas from said first separation zone, passing said gas from said first separation zone to a second compression zone and to a second cooling zone, compressing and cooling said gas in said second compression zone Aand said second cooling zone to a pressure and ternperature to condense from said gas a cold liquid hydrocarbon fraction, passing said gas and said cold liquid fraction to a second separation zone, separating uncondensed gas from said liquid fraction in said second separation zone, removing uncondensed gas from said second separation zone, contacting said uncondensed gas with a desiccant to remove water therefrom, passing said gas after removal of Water therefrom to a third cooling zone, cooling said gas in said third cooling zone to a temperature to condense from said gas a cold liquid hydrocarbon fraction, passing said gas and said cold liquid fraction to a third separation zone, separating uncondensed gas from said liquid fraction in said third separation zone, removing uncondensed gas from said third separation zone, removing said cold liquid fractions from said second and said third separation zones, passing said liquid fractions from said second and said third separation zones to a pressure reduction zone, reducing the pressure on said liquid fractions in said pressure reduction zone to separate a gas phase therefrom, removing said gas phase from said pressure reduction zone, admixing said gas phase removed from said pressure reduction zone directly with said gas entering said second compression and cooling zones, removing said cold liquid fractions from said pressure reduction zone, passing saidcold liquid fractions to said gas-liquid contact zone, passing all of said liquid fractions through said gas-liquid contact zone to a heating zone, heating said cold liquid fractions in said heating zone to stabilize said liquid fractions by vaporizing therefrom a gas phase containing undesired light hydrocarbon, passing said gas phase through said gas-liquid contact zone in countercurrent contact with only said liquid fractions passing through said gas-liquid contact zone, removing` said gas phase from said gas-liquid contact zone, passing the entire amount of said gas phase removed from said gas-liquid contact zone directly to said rst compression zone, and Vrecovering a stabilized liquid fraction from said heating zone.

3. A process for the separation and recovery of a stabilized liquid fraction from a Wet hydrooarbon gas mixture having a low pressure comprising passing a feed stream of said gas to a rst compression zone and to-a iirst cooling zone, compressing and cooling said gas in said compression zone and said cooling zone to a pressure of about S5 pounds per square inch gage and a temperature of about degrees F. to condense from said gas a liquid hydrocarbon fraction, passing said gas and said liquid fraction to a irst separation zone, separating uncondensed gas from said liquid fraction in said first separation zone, removing liquid fraction from said first separation zone, passing directly to a gas-liquid contact zone said liquid fraction at a temperature not substantially higher than its temperature in said rst separation zoneVremoving uncondensed gas from said iirs't separation zone, passing said gas from said first separation zone to a second compression zone and to a second cooling zone, compressing and cooling said gas in said second compression zone and said second cooling zone to a pressure of about 265 pounds per square inch gage and a temperature of about 95 degrees F. to condense from said gasa liquid hydrocarbon fraction, passing said gas and said liquid fraction to a second separation zone, separating uncondensed gas from said liquid fraction in said second separation zone, removing uncondensed gas from said second separation zone, removing said liquid fraction from said second separation zone, passing said liquid fraction from said second separation zone to a pressure reduction zone, reducing the pressure on said liquid fraction in said pressure reduction zone to between about a0 and 50 pounds per square inch gage to separate a gas phase therefrom, removing said gas phase from said pressure reduction zone, admixing said gas phase removed from said pressure reduction zone with said gas entering said second compression and cooling zones, removing said liquid fraction from said pressure reduction zone, passing said liquid fraction to said gas-liquid contact zone, passing said liquid fractions through said gas-liquid contact zone to a heating zone, heating said liquid fractions in said heating zone to a temperature of about 75 degrees F'. at a pressure of about 26 pounds per square inch gage to stabilize said liquid :fractions by vaporizing therefrom a gas phase containing undesired light hydrocarbon, passing said gas phase through said gas-liquid contact zone in countercurrent contact with only said liquid fractions passing through said gasliquid contact zone, removing said gas phase from said gas-liquid contact zone, passing the entire amount of said gas phase removed from said gas-liquid contact zone directly to said first compression zone, and removing a stabilize liquid traction from said heating zone.

4. A process for the separation and recovery of a stabilized liquid fraction from a wet hydrocarbon gas mixture having a low pressure comprising passing a feed stream of said gas to a first compression zone and to a rst cooling zone, compressing and cooling said gas in said compression zone and said cooling zone to a pressure of about 85 pounds per square inch gage and a temperature of about 95 degrees F. to condense from said gas a liquid hydrocarbon fraction, passing said gas and said liquid fraction to a i'st separation zone, separating uncondensed gas from said liquid fraction in said separation sone, removing liquid fraction from said first separation zone, passing directly to a gasliquid contact zone said liquid fraction at a temperature not substantially higher than its temperature in said iirst separation zone, removing uncondensed gas from said iirst separation zone, passing said gas from said first separation Zone to a second compression zone and to a second cooling Zone, compressing and cooling said gas in said second compression zone and said second cooling zone to a pressure oi about said gas in said third cooling zone to a temperature of about O degrees F. to condense from said gas a liquid hydrocarbon fraction, passing said gas and said liquid fraction to a third separation zone, separating uncondensed gas from said liquid fraction in said third separation zone, removing uncondensed gas from said third separation zone, removing said liquid fractions from said second and said third separation zones, passing said liquid fractions from said second and said third separation zones to a pressure reduction zone, reducing the pressure on said liquid fractions in said pressure reduction zone to between about 40 and 50 pounds per square inch gage to separate a gas phase therefrom, removing said gas phase from said pressure reduction zone, admixing said gas phase removed from said pressure reduction zone directly with said gas entering said second compression and cooling zones, removing said liquid fractions from said pressure reduction zone, passing said liquid fractions to said gas-liquid contact Zone, passing all of said liquid fractions through said gasliquid contact zone to a heating zone, heating said liquid fractions in said heating zone to a temperature of about 75 degrees F. at a pressure of about 26 pounds per square inch gage to stabilize said liquid fractions by Vaporizing therefrom a gas phase containing undesired light hydrocarbon, passing said gas phase through said gas-liquid Contact zone in countercurrent contact with only said liquid fractions passing through said gas-liquid contact zone, removing said gas phase from said gas-liquid contact zone, passing the entire amount of said gas phase rcrnoved from said gas-liquid contact zone directly to said iirst compression zone, and recovering a stabilized liquid fraction from said heating zone.

BRUNNER. C. BARNES.

References Cited in the le 0f this patent UNITED STATES PATENTS Number Name Date 1,313,024 Clarke et al June 7, 1931 1,976,212 Brewster Oct. 9, 1934 2,109,209 Ragatz Feb. 22, 1938 2,135,923 Throckmorton Nov. 8, 1938 2,138,218 Raigorodsky Nov. 29, 193B 2,214,678 Raigorodsky Sept. 10, 1940 2,222,275 Babcock Nov. 19, 1940 2,297,30 Hudson Oct. 6, 1942 2,342,165 Plummer Feb. 24, 1944 2,345,934 Gregory Apr. 4, 1944 

1. A PROCESS FOR THE SEPARATION AND RECOVERY OF A STABLIZIED LIQUID FRACTION FROM A WET HYDROCARBON GAS MIXTURE COMPRISING PASSING A FEED STREAM OF SAID GAS TO A FIRST COMPRESSION ZONE AND TO A FIRST COOLING ZONE, COMPRESSING AND COOLING SAID GAS IN SAID COMPRESSION ZONE AND SAID COOLING ZONE TO A PRESSURE AND TEMPERATURE TO CONDENSE FROM SAID GAS A COLD LIQUID HYDROCARBON FRACTION, PASSING SAID GAS AND SAID COLD LIQUID FRACTION TO A FIRST SEPARATION ZONE, SEPARATING UNCONDENSED GAS FROM SAID COLD LIQUID FRACTION IN SAID FIRST SEPARATION ZONE, REMOVING COLD LIQUID FRACTION FROM SAID FIRST SEPARATION ZONE, PASSING DIRECTLY TO A GAS-LIQUID CONTACT ZONE SAID COLD LIQUID FRACTION AT A TEMPERATURE NOT SUBSTANTIALLY HIGHER THAN ITS TEMPERATURE IN SAID FIRST SEPARATION ZONE, REMOVING UNCONDENSED GAS FROM SAID FIRST SEPARATION ZONE, PASSING SAID GAS FROM SAID FIRST SEPARATION ZONE TO A SECOND COMPRESSION ZONE AND TO A SECOND COOLING ZONE, COMPRESSING AND COOLING SAID GAS IN SAID SECOND COMPRESSION ZONE AND SAID SECOND COOLING ZONE TO A PRESSURE AND TEMPERATURE TO CONDENSE FROM SAID GAS A COLD LIQUID HYDROCARBON FRACTION, PASSING SAID GAS AND SAID COLD LIQUID FRACTION TO A SECOND SEPARATION ZONE, SEPARATING UNCONDENSED GAS FROM SAID LIQUID FRACTION IN SAID SECOND SEPARATION ZONE, REMOVING UNCONDENSED GAS FROM SAID SECOND SEPARATION ZONE, REMOVING SAID COLD LIQUID FRACTION FROM SAID SECOND SEPARATION ZONE, PASING SAID COLD LIQUID FRACTION FROM SAID SECOND SEPARATION ZONE TO A PRESSURE REDUCTION ZONE, REDUCING THE PRESSURE ON SAID COLD LIQUID FRACTION IN SAID PRESSURE REDUCTION ZONE TO SEPARATE A GAS PHASE THEREFROM, REMOVING SAID GAS PHASE FROM SAID PRESSURE REDUCTION ZONE, ADMIXING SAID GAS PHASE REMOVED FROM SAID PRESSURE REDUCTIN ZONE WITH SAID GAS ENTERING SAID SECOND COMPRESSION AND COOLING ZONES, REMOVING SAID LIQUID FRACTION FROM SAID PRESSURE REDUCTION ZONE, PASSING SAID LIQUID FRACTION TO SAID GAS-LIQUID CONTACT ZONE, PASSING SAID LIQUID FRACTIONS THROUGH SAID GASLIQUID CONTACT ZONE TO A HEATING ZONE, HEATING SAID LIQUID FRACTIONS IN SAID HEATING ZONE TO STABILIZE SAID LIQUID FRACTIONS BY VAPORIZING THEREFROM A GAS PHASE CONTAINNG UNDESIRED LIGHT HYDROCARBON, PASSING SAID GAS PHASE THROUGH SAID GAS-LIQUID CONTACT ZONE IN COUNTERCURRENT CONTACT WITH ONLY SAID LIQUID FRACTIONS PASSING THROUGH SAID GAS-LIQUID CONTACT ZONE, REMOVING SAID GAS PHASE FROM SAID GAS-LIQUID CONTACT ZONE, PASSING THE ENTIRE AMOUNT OF SAID GAS PHASE REMOVED FROM SAID GAS-LIQUID CONTACT ZONE DIRECTLY TO SAID FIRST COMPRESSED ZONE, AND RECOVERING A STABLIZED LIQUID FRACTION FROM SAID HEATING ZONE. 